Non Technical Summary Food and fiber production are critical ecosystem services that are of global concern. The increasing amount of food and fiber needed by the growing human population. The purpose of this project is to develop a better physiological understanding of the effects on environmental and ecological factors on net primary production, the harvest yield or fraction of NPP that is allocated to food and fiber production, and realistic assessment of the potential of management to increase production are needed to improve forecasts of potential and actual food and fiber production.

Goals / Objectives The proposed study has four objectives. (i) Compile and synthesize a NPP data base, and ancillary data, for the dominant terrestrial biomes of the world. (ii) Develop algorithms between NPP and components of NPP (e.g. bole wood production) that would allow the use of extensive, but incomplete NPP data such as Forest Inventory Analysis (FIA) to estimate NPP for larger areas. (iii) Use the compiled NPP data base to examine environmental and ecological controls on NPP, carbon allocation, and radiation use efficiency patterns both within and among biomes. Algorithms from objective 2 will be used to develop more extensive data bases that will serve as validation data for biosphere NPP models. (iv) Quantify the effects of land use change and management practices on NPP, and harvest index.

Project Methods The study will be based on 3434 NPP entries, most of which have already been entered into Access - a database manager. A summary of the data are provided in Appendix 1. The data were obtained from NPP synthesis papers and individual papers. Key NPP synthesis papers including the North American grassland NPP synthesis by Sims et al. (1978a-c), the IBP woodlands data set (DeAngelis et al. 1981), a forest NPP synthesis by Cannell (1982), a worldwide NPP synthesis by Esser et al. (1997), an arctic tundra NPP synthesis by Gilmanov and Oechel (1995), and a boreal forest synthesis by Gower et al. (2001) are the primary data sources. In addition, over the past eight years Gower has obtained copies of the original manuscripts used by the NPP synthesis papers and copies of articles that were inadvertently omitted from earlier compilations. To complete Objective #1 we must assign a vegetation classification category to each NPP site. We will use climate data provided in the paper
to classify the vegetation, but often the description of the climate of the site is limited. For the latter case, we will use a global 30-year average climate data that has a 0.5 degree x 0.5 degree resolution. We will calculate average NPP, by component, for each biome and compare the new values to existing biome averages obtained from Likens 1976. Where multiple approaches were used to estimate above- and/or belowground NPP, we will perform Meta-data analysis to ascertain if certain methods consistently underestimate or overestimate NPP. Meta-analysis requires the distillation of the results of each measurement in the form of the magnitude of the effect (i.e. measurement technique) expressed on a common scale for all observations. MetaWin 2.0 will be used for all analyses (Rosenberg et al. 2000).

Progress 10/01/02 to 09/30/05

OutputsApproximately 4100 NPP data were collected during the three year study. Prior to this study global NPP observations were based on < 500 data, with very poor coverage for tropical ecosystems. Biome averages for NPP differed dramatically between the older and revised estimates for tropical forests, with the older estimates being much greater than estimates obtained in this study, and boreal forests, with older estimates being much smaller than the estimates obtained in this study. Despite their small percent coverage of all terrestrial ecosystems, bamboo and mangrove forests had very high NPP, although not as high as tropical broad-leaf evergreen forests. Analysis of managed ecosystem NPP data clearly showed that management activities and land use changes have a far greater effect on NPP than responses of NPP to elevated CO2 experiment studies.

ImpactsThese data clearly illustrate that changes in land use (e.g. conversion from prairie to agriculture) and management practices (e.g. fertilization) have far greater effects on NPP than elevated atmospheric CO2 concentrations, suggesting more focus should be directed towards understanding land use change effects on biogeochemicstry of terrestrial ecosystems.

OutputsThe boreal forest logging studies conducted in central Saskatchewan and northern Manitoba did not show significant decreases in soil carbon content following logging, although there was evidence that detritic carbon content was redistributed from the surface litter to mineral soil. Coarse woody debris, an important component of forest carbon content, typically was greater immediately after harvest, reached a minimum approximatelt 20-40 years after harvest, and then increased.

ImpactsThe results are highly relevant to ecologists and earth system scientists modeling the global carbon cycle because many used the early NPP and carbon allocation data sets, the only ones available at the time, to parameterize and validate the NPP component of their terrestrial carbon cycling models. Additional logging studies are needed to better understand the effects of logging on soil carbon content and distribution.

OutputsForests are an important source for fiber and fuel for humans, and contain the majority of the total terrestrial carbon. The amount of carbon stored in the vegetation and soil are strongly influenced by environmental constraints on annual carbon uptake and decomposition, and time since disturbance. Increasing concentrations of atmospheric carbon dioxide, nitrogen deposition, and climate warming induced by greater greenhouse gas concentrations in the atmosphere influence carbon accumulation rates of forest, but their effects will likely differ in direction and magnitude among forest ecosystems. The net interactive effect of global change on the forest C cycle is poorly understood. The growing demand for wood fiber and fuel by humans, and the ongoing anthropogenic perturbations of the climate have changed the natural disturbance regimes (i.e. frequency and intensity) and these changes influence the net exchange of CO2 between forests and the atmosphere. Net primary
production of terrestrial ecosystems, the annual accumulation of carbon in the form of vegetation organic matter, is an important determinant of the net exchange of carbon dioxide (CO2) between terrestrial ecosystems and the atmosphere. Here we summarize NPP and carbon allocation patterns for the major terrestrial biomes of the world and show the original values significantly underestimate the carbon sink strength for many of the major terrestrial ecosystems. On average, the Whittaker and Likens biome NPP averages were 124% smaller than averages compiled in this study, with the largest discrepancies occurring for croplands (474 to 717% for temperate and tropical crops, respectively), deserts (188%) and grasslands (121 to 189% for temperate and tropical grasslands, respectively). To date, the role of forest products in the global C cycle has largely been ignored, and important emissions associated with the production, transport and utilization of the forest products have been excluded
leading to erroneous conclusions about net C storage in forest products.

ImpactsThe results are highly relevant to ecologists and earth system scientists modeling the global carbon cycle because many used the early NPP and carbon allocation data sets, the only ones available at the time, to parameterize and validate the NPP component of their terrestrial carbon cycling models.